/*
 * Copyright (c) 2005, 2013, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
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 */

package javax.xml.ws.spi;

import java.io.*;

import java.util.Properties;
import javax.xml.ws.WebServiceException;

class FactoryFinder {

  /**
   * Creates an instance of the specified class using the specified
   * <code>ClassLoader</code> object.
   *
   * @throws WebServiceException if the given class could not be found or could not be instantiated
   */
  private static Object newInstance(String className,
      ClassLoader classLoader) {
    try {
      Class spiClass = safeLoadClass(className, classLoader);
      return spiClass.newInstance();
    } catch (ClassNotFoundException x) {
      throw new WebServiceException(
          "Provider " + className + " not found", x);
    } catch (Exception x) {
      throw new WebServiceException(
          "Provider " + className + " could not be instantiated: " + x,
          x);
    }
  }

  /**
   * Finds the implementation <code>Class</code> object for the given
   * factory name, or if that fails, finds the <code>Class</code> object
   * for the given fallback class name. The arguments supplied MUST be
   * used in order. If using the first argument is successful, the second
   * one will not be used.
   * <P>
   * This method is package private so that this code can be shared.
   *
   * @param factoryId the name of the factory to find, which is a system property
   * @param fallbackClassName the implementation class name, which is to be used only if nothing
   * else is found; <code>null</code> to indicate that there is no fallback class name
   * @return the <code>Class</code> object of the specified message factory; may not be
   * <code>null</code>
   * @throws WebServiceException if there is an error
   */
  static Object find(String factoryId, String fallbackClassName) {
    if (isOsgi()) {
      return lookupUsingOSGiServiceLoader(factoryId);
    }
    ClassLoader classLoader;
    try {
      classLoader = Thread.currentThread().getContextClassLoader();
    } catch (Exception x) {
      throw new WebServiceException(x.toString(), x);
    }

    String serviceId = "META-INF/services/" + factoryId;
    // try to find services in CLASSPATH
    BufferedReader rd = null;
    try {
      InputStream is;
      if (classLoader == null) {
        is = ClassLoader.getSystemResourceAsStream(serviceId);
      } else {
        is = classLoader.getResourceAsStream(serviceId);
      }

      if (is != null) {
        rd = new BufferedReader(new InputStreamReader(is, "UTF-8"));

        String factoryClassName = rd.readLine();

        if (factoryClassName != null &&
            !"".equals(factoryClassName)) {
          return newInstance(factoryClassName, classLoader);
        }
      }
    } catch (Exception ignored) {
    } finally {
      close(rd);
    }

    // try to read from $java.home/lib/jaxws.properties
    FileInputStream inStream = null;
    try {
      String javah = System.getProperty("java.home");
      String configFile = javah + File.separator +
          "lib" + File.separator + "jaxws.properties";
      File f = new File(configFile);
      if (f.exists()) {
        Properties props = new Properties();
        inStream = new FileInputStream(f);
        props.load(inStream);
        String factoryClassName = props.getProperty(factoryId);
        return newInstance(factoryClassName, classLoader);
      }
    } catch (Exception ignored) {
    } finally {
      close(inStream);
    }

    // Use the system property
    try {
      String systemProp =
          System.getProperty(factoryId);
      if (systemProp != null) {
        return newInstance(systemProp, classLoader);
      }
    } catch (SecurityException ignored) {
    }

    if (fallbackClassName == null) {
      throw new WebServiceException(
          "Provider for " + factoryId + " cannot be found", null);
    }

    return newInstance(fallbackClassName, classLoader);
  }

  private static void close(Closeable closeable) {
    if (closeable != null) {
      try {
        closeable.close();
      } catch (IOException ignored) {
      }
    }
  }


  /**
   * Loads the class, provided that the calling thread has an access to the class being loaded.
   */
  private static Class safeLoadClass(String className, ClassLoader classLoader)
      throws ClassNotFoundException {
    try {
      // make sure that the current thread has an access to the package of the given name.
      SecurityManager s = System.getSecurityManager();
      if (s != null) {
        int i = className.lastIndexOf('.');
        if (i != -1) {
          s.checkPackageAccess(className.substring(0, i));
        }
      }

      if (classLoader == null) {
        return Class.forName(className);
      } else {
        return classLoader.loadClass(className);
      }
    } catch (SecurityException se) {
      // anyone can access the platform default factory class without permission
      if (Provider.DEFAULT_JAXWSPROVIDER.equals(className)) {
        return Class.forName(className);
      }
      throw se;
    }
  }

  private static final String OSGI_SERVICE_LOADER_CLASS_NAME = "com.sun.org.glassfish.hk2.osgiresourcelocator.ServiceLoader";

  private static boolean isOsgi() {
    try {
      Class.forName(OSGI_SERVICE_LOADER_CLASS_NAME);
      return true;
    } catch (ClassNotFoundException ignored) {
    }
    return false;
  }

  private static Object lookupUsingOSGiServiceLoader(String factoryId) {
    try {
      // Use reflection to avoid having any dependendcy on ServiceLoader class
      Class serviceClass = Class.forName(factoryId);
      Class[] args = new Class[]{serviceClass};
      Class target = Class.forName(OSGI_SERVICE_LOADER_CLASS_NAME);
      java.lang.reflect.Method m = target.getMethod("lookupProviderInstances", Class.class);
      java.util.Iterator iter = ((Iterable) m.invoke(null, (Object[]) args)).iterator();
      return iter.hasNext() ? iter.next() : null;
    } catch (Exception ignored) {
      // log and continue
      return null;
    }
  }

}
